Skip to content

Add your earlier progress to your account?

From before you signed in, this browser has:

Which plan do you want to keep?

You answered the plan questions before you signed in, and those answers don't match the plan saved on your account.

SettingSaved planNew answers

Study progress is waiting to be saved

Cells in the sediment

16 min

Skills you'll build4 skills
  • Recognize urinary acanthocytes and their glomerular association
  • Select an optical method for faint structures in unstained urine
  • Read many squamous cells as a sign of a poorly collected urine specimen
  • Recognize renal tubular cells and report them as a sign of tubular injury

At the bench: Identify and report cells, casts, crystals, and other urine sediment findings · Reconcile urine appearance, chemistry, and microscopy findings

Try first

Try first

Two fresh urine sediments are on the microscope. In the first, some red cells are rings with small round blebs budding from the membrane. In the second, a concentrated urine with specific gravity 1.030, the red cells are shrunken with evenly spaced spikes all around. Which finding supports bleeding from the glomerulus?

Keep going to see the reasoning.

Keep going to see the reasoning.

Right. Keep going to follow the reasoning.

Keep going to see the reasoning.

Get the idea

Use the explanation to check your first decision.

Setting the light

Most unstained sediment particles have little contrast. In bright field, lower the light before scanning. Full illumination washes out hyaline casts and pale ghost red cells. Phase contrast makes these faint structures stand out and preserves the red cell shapes needed to judge dysmorphism. A supravital stain or a validated stain adds nuclear detail to a round cell that is difficult to identify.1,3

Dysmorphic red cells

Fresh red cells in urine are smooth discs about 6 to 7 µm across. Concentrated urine crenates them, and dilute urine swells them into pale ghosts. Acanthocytes are ring forms with one or more membrane blebs. A pattern of acanthocytes or other dysmorphic red cells in a fresh specimen supports glomerular bleeding. Assess it on enough red cells for a representative percentage, and interpret it with the protein result and the casts.1,2

Squamous cells describe the collection

Squamous cells come from the distal urethra and the genital skin. Many of them, with bacteria and mucus, suggest a poorly collected specimen. They cannot show which organisms in a culture are contaminants.1

Renal tubular epithelial cells

Renal tubular epithelial cells line the nephron. Proximal cells are large and coarsely granular. Distal cells are smaller and round, with an eccentric nucleus. The round ones are the cells most often miscounted as white cells. Increased tubular cells, or tubular cells inside casts, support tubular injury.1,2

CellAppearanceWhat it indicates
Crenated red cellShrunken disc with even spikesConcentrated urine
AcanthocyteRing form with membrane blebsGlomerular bleeding
NeutrophilAbout 12 µm, granular cytoplasm, lobed nucleusInflammation somewhere in the tract
Renal tubular cellLarger than a neutrophil, one round eccentric nucleusTubular injury
Squamous cellVery large, flat, small central nucleusCollection quality

A single feature rarely identifies a cell. Size, outline, nucleus, texture and the urine around the cell are assessed together.3

Follow the bench demonstration

Sources for this step
References
  1. Kouri TT, Hofmann W, Falbo R, et al. The EFLM European urinalysis guideline 2023. Clin Chem Lab Med. 2024;62(9):1653-1786. doi:10.1515/cclm-2024-0070
  2. Cavanaugh C, Perazella MA. Urine sediment examination in the diagnosis and management of kidney disease: Core Curriculum 2019. Am J Kidney Dis. 2019;73(2):258-272. doi:10.1053/j.ajkd.2018.07.012
  3. Strasinger SK, Di Lorenzo MS. Urinalysis and Body Fluids. 7th ed. F.A. Davis; 2021. ISBN 978-0-8036-7582-7. F.A. Davis catalog record.

Watch one

Read each decision and its explanation.

A random urine comes from a hospitalized man whose creatinine has doubled in two days. The strip shows protein 1+, blood negative and leukocyte esterase negative. At high power you see many round cells with granular cytoplasm. What are they?

  1. Scan at low power with the light turned down. Several granular casts are present, and some casts hold round cells.

    Casts and their contents are found at low power, and faint structures disappear under full light.

  2. Compare size at high power: the round cells are clearly larger than the few neutrophils in the field.

    A neutrophil is about 12 µm, so size is compared with a known cell first.

  3. Look at the nucleus: each cell has one round nucleus placed to one side.

    A lobed nucleus identifies a neutrophil. One round eccentric nucleus fits a distal tubular cell.

  4. Check the strip: leukocyte esterase is negative, which does not fit a sediment full of white cells.

    Leukocyte esterase detects the enzyme in neutrophils, so many white cells would usually turn it positive.

  5. Confirm the identification: the same cells sit inside casts, and phase contrast shows the single nucleus clearly.

    Cells inside a cast come from the tubule, and a stain or phase contrast shows nuclear detail when the identification is uncertain.

They are renal tubular epithelial cells. Report them as tubular cells, with the casts that contain them, as the procedure specifies.

Practice this skill

Your turn

Problem 1 of 3 · Hints available

Point to a panel of red cells whose shape supports bleeding from the glomerulus.

Four unlabeled urine sediment photomicrographs in two rows of two.

Image sources and licenses

  1. Top left
  2. Top right
  3. Bottom left
  4. Bottom right
Hint
  1. The shape change that matters comes from the cell's passage through the kidney.
  2. Smooth round discs are the same regardless of where the bleeding started.
Show the answer

Acanthocytes, Dysmorphic red cells

Acanthocytes and other dysmorphic red cells support glomerular bleeding. Isomorphic red cells can come from anywhere in the tract. Budding yeast are red cell look-alikes.

Review Red blood cells

Problem 2 of 3 · Hints available

A voided urine specimen has abundant squamous epithelial cells. What can the laboratory conclude from that finding alone?

Squamous cells alone cannot predict that every cultured organism is a contaminant.

Squamous cells can reflect genital or distal urethral material. Interpret them with collection quality, bacteria, and other findings.

Renal tubular epithelial cells and their casts support tubular injury. Squamous cells arise farther downstream.

Hint
  1. Consider where squamous cells come from.
  2. A cell count describes the specimen. A culture result describes each organism grown.

Review Epithelial cells and lipid

Problem 3 of 3 · On your own

A urine with protein 2+ is scanned at low power in bright field with the condenser wide open and full light. No casts are seen in 10 fields. What do you do before reporting?

Casts are found at low power, where the whole field is surveyed. A higher objective covers far less of the slide and still misses faint casts under full light.

Reduced light or phase contrast brings faint hyaline casts into view. With protein 2+, casts are worth a careful second look.

Full light washes out hyaline casts, whose refractive index is close to that of urine. Ten fields is the correct number. The full light obscured the casts.

Missed a faint cast under bright illumination

Hyaline casts and ghost RBCs have a refractive index close to urine, and excess bright-field light washes them out. Scanning with full illumination undercounts casts that reduced light or phase contrast would show.

Stain can help, and it is added to a portion of the sediment according to the procedure. The lighting that obscured the casts is corrected first.

Review Optical methods

Use it

Read the case evidence, then make each decision. The step is complete without it.

  • Ilse Stirling, 67, is on a medical floor after a contrast scan. Her creatinine rose from 0.9 to 1.8 mg/dL over two days.
  • She collected a voided urine without cleansing, and it reached the laboratory within 1 hour.
  • Strip: protein 1+, blood trace, nitrite negative, leukocyte esterase negative.
  • Sediment: many squamous cells, many bacteria, mucus threads.
  • Also present: many round cells with one eccentric nucleus, some inside granular casts.
Decision 1 of 2

How do you report the round cells?

The eccentric nucleus, the negative esterase and the cells inside casts place them in the tubule.

A single eccentric nucleus and a negative leukocyte esterase do not fit neutrophils. Counting them as white cells omits the tubular injury and suggests infection.

Called a renal tubular cell a white cell or urothelial cell

Round renal tubular cells resemble white cells, macrophages, and deep urothelial cells. Counting them as white cells hides evidence of tubular injury and can suggest infection. Nuclear position, cytoplasmic texture, phase contrast, or a validated stain separates them.

Squamous cells are very large and flat with a small central nucleus. These round cells are much smaller and are also inside casts.

Review Epithelial cells and lipid

Decision 2 of 2

The nurse asks whether the squamous cells mean the whole urinalysis is contamination. What do you do with the report?

The tubular cells and casts came from her kidney and describe the injury now. A recollection can be requested for the bacteria, and the renal findings are still reported.

The squamous cells describe the collection. Genital material cannot put tubular cells inside casts, so the renal findings stand and are reported.

Squamous cells cannot show which organisms are contaminants. Only the collection quality is in question.

Called a culture contaminated from squamous cells

Abundant squamous cells suggest genital or distal urethral material, especially with bacteria and mucus. They cannot show which cultured organisms are contaminants. Declaring the culture contaminated from the squamous cells alone can dismiss a true pathogen.

Review Epithelial cells and lipid

The key finding is the tubular cells inside casts. Contamination adds squamous cells, bacteria and mucus, and it does not form casts. The casts place those cells in her kidney, and the report includes them with a comment on the collection.

For reference

Sources checked